Direction finding system



Nov. 7, 1950 A. G. RICHARDSON ETAL DIRECTION FINDING SYSTEM Filed Dec. l, 1947 2 Sheets-Sheet 1 Nov. 7, 1950 Filed Dec. l, 1947 A. G. RICHARDSON ETAL DIRECTION FINDING SYSTEM 2 sheets-sheet? IN VEN TORJl Army G. /P/cfM/Poso/v F/P/l/v/f 0. c/u/ fsas A TTOEN/E'Y Patented Nev. 7, 195o UNI-TEU STATES vFATF.NTLformel:

DIRECTION FINDING SYSTEM .Avery Groat `Richardson, Boonton, N. J., and Frank 0. Chesus, Bayport, N. Y., assignors to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application December 1, 1947, Serial No. 789,060

13 claims. (C1. 343-106) This invention relates to radio range systems, particularly of the type where the transmitter comprises a plurality of antenna systems and the receiver a single antenna system.

Briefly the system to which this invention relates involves a radio beacon using a large spacing between several antennae and generating a cardioidshaped radiation pattern provided with a reference mark for determining the bearings of a receiver withrespect to the beacon. The rotating pattern is obtained by combining the radiationield of four Adcock antennae operating at different frequencies and modulated with voltages which are in phase quadrature, with the radiation pattern of an antenna operating at still a different frequency and also modulated with a voltage which serves as a modulation phase reference. A receiver suitable for use with a radio beacon of this type comprises a single antenna and two I. F. channels and one low frequency goniometer and synchronized indicator.

An `object of this invention is to provide an improved radio range system which will give an instantaneous indication with a high degree of accuracy in the ultra high frequencyranges.

Another object of this invention is to make the.

transmitter a multiple antenna system and/or a receiverv a single antenna system, the trans.-

mitter antennae being operated at different car'-` rier frequencies.

Another object of this inveuonis to pmx/nie,

a radio range system wherebyseparate signals' for audio channels may be simultaneously trans- 2 tenna 5 is the sense antenna. Each of these ve antennae transmits a non-directional ultra high frequency carrier of a different wave-length. The carrier of each antenna is modulated 'by energy from sources of va lower frequency, having different phase relation as indicated in degrees from the output leads of the low frequency phasingcircuits 'l and 8. The antennae I, 2, 3 and i are spaced from each other less than one quarter of the wavelength of the modulating frequency. Ultra high frequency oscillators 9, I0, II, I2 and I3, provide different frequencies suiciently separated asnot to interfere with each other or with the low frequency modulating energy or any audioor signal frequency which may be transmitted over any one or all of the antennae. For example, the frequency FN of generator 9 may be 100 megacycles, FS of generator II may be 100.01megacycles, FE of generator I2 100.05

served' na cathodefray screen of the direction indicator.

yThe above mentioned and other features and objects of this invention will become more apparent and the invention itself though not necessarily dened by said features and objects will be best understood by reference to the following description of an embodiment of the invention taken in connection with the accompanying drawings wherein:

Fig. 1 illustrates a schematic block wiring diagram of a transmitter system incorporating features of my invention; and

Fig. V2 illustrates a receiver used in conjunction with the embodiment described in Figure 1.

Fig. 1 shows a transmitting system having five ultra high frequency antennae I, 2, 3, Il and 5.

One pair o f antennae I, 2 are designated as north and south and the other pair, quadrature spaced frequency. Because of the phasing an effective are modulated in the same phase.

megacycles and FW of generator I3 105.01 megacycles.

The* diiferences between the frequency of FN and FS or FE vand FW should be small with respectA to that betWeenFN and FE for reasons which willY later be described in connection with 3 tennas ismodulated with a lower frequency wave,

say for example, a-200 cycle sine wave from low frequency oscillator 6 which is connected to the low, frequency Vphasing units T, l8 and I4.

.Oscillator 9 and sense antenna oscillator I0 This is for the purpose of providing a reference mark for determiningthe bearing of the receiver with respect to the beacon. However, the reference mark may be located at any desired phase point. The

,north and south antennae I, 2 are shown to be phased 180 .apartv in their modulation frequency.

Similarly, antennas 3 and 4 are phased 180 apart and also 90 out of phase with respect to I-and 2. This provides four different phases of low frequency energization for each of the four antermale;` `corresponding to the four directions of the compass.k The voltages from the four antennae .taken together with the voltage from the sense'antennaecombine to give an effective cardioid shapedfpattern at the common modulation rotation of the cardioid is produced of which the null will be apparent in the receiver at an angle with respect to the transmitting system dependcnt upon the position of the receiver.

In the event there is any difference in the strengths of the antennae `fields. an'automatic volume control system incorporated in the receiver acts to overcome such adiierence by adjusting the output at each IF stage of the receiver to be of the same voltage.

Referring now to the receiver diagram shown' in Figure 2, there is provided a single omnidirectional antenna 2Q. Antenna 20 is connected to an ultra high frequency 'broadbandamplifler mixer circuit ZI, which may be Yalsuperheterodyne circuit with a beatingoscillator 22.V From this broad band receiver 2| the `energy is transmitted to one or more separate IF amplifiers. If the difference between the .frequencies of FN .and FS or FE and FW is vsufficiently small with respect to that between FN and FE, then the FN and FS channel may be combined in one .amplier stage 23 and the FE and FW channel may be combined in another amplifier stage 24 while the-sense antenna F may be amplified in a third stage 2.5. However, if there is sufficient difference .of frequency between the various channels, separate IF amplifiers may be provided for eachone of the five separate carrier frequencies. Each of these ampliiiers 23, 24 and 25 is controlledby separate automatic volume control circuits 2S, 27 andA 28 which may be adjusted to give the same constant outputregardless of the amplitude Vor voltage of the received signal.

The output of each'IF amplifier 23, 24 and 25 is coupledto a separate IF detector stage 29, 30 and SI each of ywhich comprises a diode rectifier tube with a-cathode bias Aresistor to ground. The IF detectors 29 -andareconnected together at 32 and jointly coupledto anamplifier circuit 33 and a 90 phase shifter-34.` LI'he output of circuits 33' and 34 areappliedto the` stator coils 35 and 36 respectively of a low-frequency 4goniometer 31 to produce a rotating iield at thespeed of a modular tion frequency determined by the speed of rota tion of the driving means 38. The output from the sense IF ampliiier 2-5 'and detector 3 Iis applied to the rotor coil 39 ofgoniometer 31. f

The rotor coil S9 is continuously rotated by driving means 38 so that a voltage -is induced in coil 39 which -variesfin phase determined by the position of the rotor 39 with respect to the stators and 36. By applying the 'sense voltage, in phase with the north modulated signal, over circuit 25, and detector 3| to the rotating coil 39, a resultant voltage is obtained which is inverted in the circuit lrand applied to an indicator 4 I. The turning of the rotor is synchronized With the direction indicator 4I which may be a phase meter, or a cathode ray oscilloscope, as-shown, having a screen upon which an' inverted kvcardioid pattern 42 is indicated. The position of the plane with respect to the azimuthfposition aroundthe transmitting location willy determine-where the' null positienoi thegoniometer rotor occurs. The indication will have only onenull so that sense will be automatic and continuous,

The output of the IF amplier A23 is connected to detectors 43 and 44, separately tuned to each of the two frequencies FN and FS, which are respectively connected to audio receivers 45 and 46. Similarly the IF amplifier 24 may be coupled to east and west detectors not shown and the sense IF amplifier Z5 may .also have a detector connected to it. Thus the transmitter that is used for either the center antenna or the array antennae can also be modulated by voice for communication purposes without any disturbance to the bearing indicator. To line 4l from the circuit 46 there is connected broad band IF detector 48 .to indicate. whether any one of the channels to the ve different antennae is carrying an audio frequency signal. A monitoring audio receiver 49 is coupled to the output of broad band detector 48.

The circuits of the receiver may be preset so that corresponding frequency separations at different beacons are selected by a simple control such as a push button-.or dial; For instance, an operator flying a course would select an approaching airport `'frequency along route, identify his position, followhis. route from the radiorange bearing and if need be establish contact over the same receiver and transmitter set-up withoutany change of vfrequency or adjustment. Airports sufficiently far apart could use the same ultra high frequency without interference,

The omnidirectional range herein disclosedy provides a system aording ease of maintenance, low installation cost, ease of operation, accuracy of bearing indication, high-degree of stability and a good communication intelligence.

While we have described above the principles of our invention in connection with specic apparatus and particular modications thereof, itis to be clearly understood that this description is made only by way oi example and-not as a limitai tion on the scope of lour invention. I

What is claimed is: v p f l. In a radio transmitting system, means for producing a rotating directional radiant energy iield comprising means for producing aradiant energy field, said radiantl energy eld comprising component,omnidirectional iields of different frequencies, means for varying the intensity of said component elds to 'effect said rotating directional eld, f p2. A system as set forth in claim l, wherein means for. producing said component fields cornprises twO Dals o f quadraturespaced antennas operating at diierent radiol frequencies, and said intensity varying means comprises means for modulating each of said component fields in accordance with voltages which are substantially in phase quadrature relation to produce a rotating directional field.

3. A receiver v system for indicating direction with respect to a transmitter system wherein a plurality of radiations of different radio frequencies are varied in intensity in a predetermined manner by a common modulating frequency, comprising means for receiving and segregating said different radiations, means for detecting said separated radiations to derive the modulation signals and means responsive to the detected modulation signals vfor indicating said direction.

4. In a radio range, means for producing a rotating directional Vradiant energy eld comprising means for producing a radiant energy rleld, said radiant energy field producing means comprising two pairs of quadrature spaced antennas and a sense antenna operating at diiTerent c arrier frequencies, means for varying the intensity of-.the radiant energy. supplied yto adjacent.. ones of said .antennas substantially in phase quadra-l tureftouproduce said.. rotating directional field,

meanSfOr varyingk the. intensity'of vthe Vradiant energy supplied to `said sense `antenna. with a given voltage. having iapredeterminedfphase rer` lationship .withs'aid rotatingeld whereby a rotating directionalV eld liavinaiseiise direction is produced.

5. A system as seti'forthinlclaim 4, further comprising means for modulating saidL different frequencies with other signals, means located at said remote receiver for detecting said other signals.

6. A system as set forth inclaim 4 wherein said indicator comprises .av4 cathode .ray oscilloscope and said direction is visually indicatedas an inverted cardioid pattern on the screen of said oscilloscope.

7. In a radio range system, means for produc,- ing a rotating directional radiant energy field comprising means for producing omnidirectional component fields of different frequencies, means for varying the intensity of said component fields to effect said rotating directional field, and means for modulating the energy of each of said component fields with other signals.

8. A radio range system comprising means forA producing a radiant energy eld, said field comprising omnidirectional component fields of different frequencies, means for varying the intensity of said component elds to effect said rotating directional field, means for modulating the energy of each of said component elds with individual signals, omnidirectional antenna means for receiving energy f said frequencies, means coupled to said antenna means for separating said frequencies, means for detecting and indicating said individual signals from said separated frequencies, means for detecting and combining said separated frequencies to produce quadrature phase spaced voltages, a goniometer, means for applying said voltages to said goniometer, and bearing indicating means coupled to said goniometer for indicating said receiving means position.

9. A receiving system for indicating direction with respect to a transmitter4 system, wherein a plurality of radiations of different radio frequencies and asense frequency radiation are varied in intensity in a predetermined manner by a common modulating frequency to produce a rotating directional eld radiation pattern comprising lantenna means for receiving energy of said frequencies, a goniometer, and an indicator, means coupled to said antenna means for separating said plurality of frequencies, means for detecting and combining said separated frequencies to produce quadrature phase spaced signals, means for applying said quadrature phase spaced signals to the stators of said goniometer, means coupled to said antenna means for applying said sense frequency to the rotor of said goniometer, means for rotating said rotor at a modulation frequency, meansV for synchronizing said indicator means with said rotating means, and means for applying said modulated rotor output to said indicator means whereby the direction of said rotating field producing means is indicated.

10. A receiving system for indicating direction with respect to a transmitter system, wherein a plurality of radiations of different radio frequencies and a sense frequency radiation are varied in intensity in a predetermined manner by a common modulating frequency to produce Bf a lrotating directional eldradiation .pattern coniprisingxfia fsingle'. omnidirectional antenna, '.a goniometer, and. an indicator,` intermediateire`-..r quency channels forleachof said frequencies, each .rofssaidlintermediate frequency .channels comprising. automatic. .Volume control means,` means for couplingsaid .antenna to the input of" said channels. means 'for `detecting and combin-` ing-l the output of `l said-.channels receivingisaidi` pluralityV of ffrequencies. tof-.produce l quadrature phaseispaced signals, meansfor applying said;

quadrature phaseispaced signals.l to thestatorsi ofsaid goniometer, means for. applying the. inter-r mediate frequency output of saidsensefrequency;

, totherotorof saidgoniometer, means for rotat;

quency to produce a rotating directional field radiation, said receiver comprising omnidirecytional antenna means for receiving energy of said frequencies, a radio goniometer, an indicator means, means coupled to Said antenna means for separating said plurality of frequencies, means for detecting and combining said separated frequencies to produce quadrature phase spaced signals, means for applying said quadrature phase spaced signals to the stators of said goniometer, means coupled to said antenna means for applying said sense frequency to the rotor of said goniometer, means for rotating said rotor at a modulation frequency, means for synchronizing t said indicator means with said rotating means and means for applying said modulated rotor output to said indicator means whereby the direction of said rotating field producing means is indicated.

12. A transmitter system, and a receiving system for indicating direction with respect to said transmitter system, said transmitter system comprising'means for producing a plurality of radiations of different radio frequencies and a sense frequency radiation, means for varying the inf tensity of all of said radiations in a predetermined manner by a common modulating frequency, to produce a rotating directional field radiation pattern, said receiver comprising antenna means for receiving energy of said frequencies, a eld producing device, means coupled to said antenna means for separating said frequencies, means for detecting and combining said separated frequencies to produce phase spaced signals, means for applying said phase vspaced signals to said field producing device, whereby a resultant eld is obtained having a field strength pattern descriptive of said rotating pattern, means for searching said resultant eld whereby the direction of said rotating field. producing means is indicated.

13. A transmitter system, and a receiving system for indicating direction with respect to said transmitter system, said transmitter system comprising means for producing a plurality of radiations of different radio frequencies and a sense 7 frequency radiation, means for varying the .intensity of all of said radiations in a predetermined manner by a common modulating frequency to produce ay rotating directional eld radiation, said receiver comprising a single omnidirectional antennaa radio goniometer, an indicator means, intermediate frequency channels or each of saidfrequencies, each of said channels comprising automatic volume control means, means for coupling said-antenna to the input of said channels, means for detecting and combining the outputs of each of said channels receiving said plurality of frequencies to produce quadrature phase spaced signals, means for applying said quadrature phase spaced signals to the stators of said goniometer, means for applyin'g the intermediate frequency output of said sense frequency to the rotor of said goniometer,

means for rotating said rotor at a modulation frequency, means for synchronizing said indicator means with said rotating means and means forapplying said modulated rotor output to said indicator means whereby the direction of said rotating eld producing means is indicated. AVERY GROAT RICHARDSON. FRANK O. CHESUS.

REFERENCES CITED The following references are of record in the le of this patent: v

UNITED STATES PATENTS Number Name Date 2,288,815 Luck July '7, 1942 2,438,946 Richardson et a1. Apr. 6, 1948 

